Back at IDF 2010, we wrote about Intel Light Peak nearing its eventual launch in 2011. Back then, the story was a 10 Gbps or faster physical link tunneling virtually every protocol under the sun over optical fiber. Though an optical physical layer provided the speed, in reality the connector and physical layer itself wasn’t as important as the tunneling and signaling going on beneath it. The dream was to provide a unified interface with enough bandwidth to satisfy virtually everything desktop users need at the same time - DVI, HDMI, DisplayPort, USB, FireWire, SATA, you name it. Daisy chain devices together, and connect everything with one unified connector and port. At IDF, we saw it moving data around between an Avid HD I/O box, a Western Digital external RAID array, and simultaneously outputting audio and video over HDMI. Intel also had another live demo working at over 6.5 Gbps. 

That dream lives on today, but sans optical fiber and under a different name. Intel’s codename “Light Peak” is now named Thunderbolt. In addition, instead of optical fiber, ordinary copper does an adequate enough job until suitably cheap optical components are available. It’s a bit tough to swallow that optical fiber for the desktop still isn’t quite ready for mainstream consumption - issues like bend radius and the proper connectors were already mitigated - but copper is good enough in the meantime. Thunderbolt launched with the 2011 MacBook Pro, and though the interface isn’t Apple exclusive, will likely not see adoption in the PC space until 2012. 

Although Thunderbolt in its launch instantiation is electrical, future versions will move to and support optical connections. When the transition to optical takes place, legacy electrical connector devices will work through cables with an electro-optical transceiver on the cable ends so there won’t be any need to use two separate kinds of cables. The optical version of Thunderbolt is allegedly coming later this year. 

Thunderbolt shares the same connectors and cabling with mini DisplayPort, however Thunderbolt cables have different, tighter design requirements to fully support Thunderbolt signaling. DisplayPort is an interesting choice since it’s already one of the fastest (if not the fastest) desktop interfaces, topping out at 17.28 Gbps in DisplayPort 1.2 at lengths of under 3 meters. At longer distances, physics rears its ugly head, and throughput drops off over electrical links. Of course, the eventual advantages of moving to photons instead of electrons are greater distance without picking up much latency. 

Thunderbolt is dual-channel, with each channel supporting 10 Gbps of bidirectional bandwidth. That’s a potential 20 Gbps of upstream and 20 Gbps of downstream bandwidth. The connection supports a daisy chain topology, and Thunderbolt also supports power over the cable, 10W to be precise. We aren't sure at this time what the breakdown on voltage/amperage is though.

Back when it was Light Peak, the goal was to tunnel every protocol under the sun over a common fast link. Multiplex everything together over one protocol-agnostic link, and then you could drop relevant data for each peripheral at each device in the daisy chain. Up to 2 high-resolution DisplayPort 1.1a displays and 7 total devices can be daisy chained. Thunderbolt instead carries just two protocols - DisplayPort and PCI Express. Tunnel a PCIe lane over the link, and you can dump it out on a peripheral and use a local SATA, FireWire, USB, or Gigabit ethernet controller to do the heavy lifting. Essentially any PCI Express controller can be combined with the Thunderbolt controller to act like an adapter. If you want video from the GPU, a separate dedicated DisplayPort link will work as well. Looking at the topology, a 4x PCI Express link is required in addition to a direct DisplayPort connection from the GPU. 

Apple learned its lesson after FireWire licensing slowed adoption - the Thunderbolt port and controller specification are entirely Intel’s. Similarly, there’s no per-port licensing fee or royalty for peripheral manufacturers to use the port or the Thunderbolt controller. iFixit beat Anand and me to tearing down the 2011 MacBook Pro (though I did have one open, and was hastily cramming my OptiBay+SSD and HDD combo inside) and already got a shot of Intel's Thunderbolt controller, which itself is large enough to be unmistakable:

Thunderbolt Controller IC on 15" 2011 MacBook Pro - Courtesy iFixit 

In addition, you can still plug normal mini Display Port devices into Thunderbolt ports and just drive video if you so choose. 

Though there aren’t any Thunderbolt compatible peripherals on the market right now, Western Digital, LaCie, and Promise have announced storage solutions with Thunderbolt support. Further, a number of media creation vendors have announced or already demonstrated support, like the Avid HD I/O box we saw at IDF. 

Thunderbolt already faces competition from 4.8 Gbps USB 3.0 which has already seen a lot of adoption on the PC side. The parallels between USB 2.0 / FireWire and USB 3.0 / Thunderbolt are difficult to ignore, and ultimately peripheral availability and noticeable speed differences will sell one over the other in the long run. Moving forwards, it’ll be interesting to see Thunderbolt finally realize the “light” part of Light Peak’s codename, and exactly how that transition works out for the fledgling interface.

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  • Penti - Wednesday, March 2, 2011 - link

    Yes of course, and it's not always you need it for gaming.

    But Thunderbolt isn't a replacement for real external PCIe interfaces for graphics. Having external PCIe 2.0 x2 devices for storage is great though. In servers there might be some merit to x8 cards but here 2 PCI-e 2.0 lanes should be more then fine. By a lot. It's enough for a high-end video work-flow any way. Definitively a more professional setup then to go with NEC or whatever USB 3.0 chip. Which there is still no OS X software stack for any way. From Apple. Lacie has release a third party driver though. For those that can extend their system using ExpressCard or future Thunderbolt > USB 3 converters. (Or by PCIe cards).
  • FXi - Friday, February 25, 2011 - link

    If this was coming on motherboards a month or two from now, I could understand the hoopla. But this won't be in laptops you can BUY for a year, quite likely a bit more than a year. So why the hoopla?

    It's a delaying tactic. USB 3 is here. It works. And yes, it could transmit video if you so chose, and you wouldn't notice the diffrence between 5Gb/s and 10Gb/s. Quite likely the speed of Intel's solution is sensitive to cable quality and length, so I'm not even sure calling it a 10Gb/s connection is really reasonable in most consumer level solutions and situations. But that's fine.

    Intel, come see us in a year or so when you have a product to SELL. And it'll be a year (2 years from now mind you) before you'll see this interface widespread in actual devices.

    So nice technology demonstration. The product will be interesting when it gets here, but it is largely irrelevant to this year let alone next.
  • softdrinkviking - Friday, February 25, 2011 - link

    i suggests you read the coverage of the new macbook pro line-up!
  • AnnonymousCoward - Monday, February 28, 2011 - link

    Yeah USB3 streams Blu-Ray just fine and it's very hard to saturate its 400MB/s throughput. Matching a displayport + x4 PCIe makes little sense to me.
  • ninjit - Friday, February 25, 2011 - link

    In the article you state...
    "Thunderbolt is dual-channel, with each channel supporting 10 Gbps of bidirectional bandwidth. That’s a potential 20 Gbps of upstream and 20 Gbps of downstream bandwidth"

    I don't believe that's correct.
    I think it means you can have 10Gbps streams going up and down simultaneously.

    There's no mention of 20 Gbps on the intel or apple pages about the tech - if it was capable of pushing that many bits one-way, you think they would be marketing it as such.

    This is what intel says about the throughput:
    "Dual-channel 10 Gbps per port, Bi-directional"
    and Apple states:
    "Thunderbolt I/O technology gives you two channels on the same connector with 10 Gbps of throughput in both directions."

    To me this means there are 2 channels of 10 Gbps each, one up and one down.
  • regli - Saturday, February 26, 2011 - link

    I believe that he is correct. Intel states the following:

    A Thunderbolt connector is capable of providing two full-duplex
    channels. Each channel provides bi-directional 10 Gbps of bandwidth.

    This adds up to 20 Gb/s each way. Based on Stephen Foskett's input

    you can even add "plus up to two DisplayPort v1.1a connections with 8.64 Gb/s each".
  • iwod - Saturday, February 26, 2011 - link

    Since Thunderbolt provide enough power for both SSD, HDD and DVDs, wouldn't it be better to used Thunderbolt internally as well?

    Once PCI - Express 3.0 lands and we have enough bandwidth head room, this is truely one port to rule them all.
  • jcandle - Monday, February 28, 2011 - link

    That really isn't the issue. If you look at Intel's datasheet you see that devices use their native PCIe drivers. That means each device would essentially be a PCIe device. Thunderbolt essentially wraps the PCIe signal making it transparent to the end device. The device simply thinks its directly connected to the PCIe bus, just like an internal PCIe add-on card is connected today. Thus, this would be similar to the existing PCIe SSD units already being sold. And would likely require drivers for every manufacturer's controller unless already bundled with the OS. This also inflates the cost of each component. The internal SATA controller on your chipset provides multiple port defraying the cost of implementing a device. Having an internal DVD on thunderbolt serves no purpose than to inflate its cost and implementation. That said, future IO devices after current optical drives have been phased out, may use a more evolved version of thunderbolt to internally connect.

    Thunderbolt is most useful in external situations because computers are shrinking for the large workstation towers of old to new slimmer form factors. Thunderbolt makes it practical for machines with less internal space to host a variety of high performance peripherals and add-ons.
  • newonanand - Monday, February 28, 2011 - link

    if thunderbolt can run as networking and it has native driver supports, it will definitely benefits server products for small business/ home business.

    Think about setup like Mac mini Server -> Promise RAID -> Mac mini Server running Parallel Server for Mac.

    The point is the Mac comes with ThunderBolt FREE. 10Gb Ethernet is still VERY EXPENSIVE for now.
  • jcandle - Monday, February 28, 2011 - link

    Direct connection is likely out of the question, but it could be proxied through thunderbolt to thunderbolt transfer cable; similar to the usb to usb transfer cables already available. However, its cost would be similar to the existing usb solution and thus make it costly to link multiple computers together; costly, in comparison to existing GbE.

    Still I agree it would be cheaper than current 10GbE. However, if for no other reason that simple demand-- if consumers desire greater bandwidth than current GbE it would drive down the cost of 10GbE. Currently the majority of 10GbE cost lies in its switches; "dumb" switches would need to be developed to fill this need.

    There is one note about your example. You have two computers sharing one RAID. That doesn't work. The same issue already occurs with enterprise customers with FC RAIDs that want to share it between two workstations. You need a special file system and locks to prevent each computer from corrupting data on the device. Or you have to set up two separate "partitions" thus making two separate RAIDs. The simplest solution for consumers is to have the RAID be a special NAS with each computer having a driver to access the NAS in a network like fashion. I don't expect such a solution to come cheaply.

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